1. Field of the Invention
The present invention is directed to the field of multiplex type communication systems and more specifically to a medium for transmitting both mechanical and electrical energy between the elements of said system.
2. Description of the Prior Art
Presently, the electrical systems of most vehicles utilize individual wires to carry electrical energy between each controlling switch and its designated load. For instance, the numerous types of loads on the rear of a vehicle may include running lights, left turn signals, right turn signals, backup lights, stop lights and rear window defroster. Each type of load conventionally requires individual control wires connecting it to a corresponding switch located near the vehicle operator's seating position. The aggregate of wiring, as a result of the conventional approach, effects substantial penalties in terms of: material costs; complexity of fabrication; space dedication; and vehicle weight.
Several types of electrical systems have been proposed which are directed to achieving a substantial reduction in the wiring content of a vehicle. A good review of those systems is contained in a paper entitled "Time-Shared Multiplexing System Applied to Motor Vehicles" by L. J. Neveti; published by the Society of Automotive Engineering, Inc., Feb. 23, 1976, as Paper No. 760,181; and incorporated herein by reference. The systems described in the Neveti paper utilize at least a heavy gauge busbar type power cable ringing the vehicle and one or more of a light gauge electrical cable or fiber optic bundle running parallel to the power cable. In one instance, a frequency selective system is described which utilizes a power carrying busbar that is said to also transmit electromagnetic audio frequencies. In those instances where command signals are electrically transmitted from the command module to an appropriate receiver, there is a great potential for spurious signal introduction and electromagnetic interference (EMI) on the signal carrying medium that will affect the command signal reception. On the other hand, while the fiber optic medium for carrying the control signals overcomes the spurious signal and EMI problems of electrical command conductors, and is lighter than most conducting mediums, termination problems exist which are said to outweigh the advantages of using the fiber optic bundle as a command signal transmitting medium on vehicles.